The removal of unwanted hair growth from the body can be accomplished with mechanized means, for example razors, tweezers or wax, all of which are uncomfortable to use, irritate the skin and/or cause damage to the skin. Another form of hair removal is by heating the hair growth to a temperature sufficient to cut the hair, however a concern of devices for hair removal involving heat is the danger of skin damage from excess heat. U.S. Pat. No. 6,825,445, issued Nov. 30, 2004 to Shalev et al., the entire contents of which is incorporated herein by reference, is addressed to an electric shaver comprising a heat generator and one or more heat elements heated to a temperature sufficient to cut hair, the heat generator arranged to prevent heat from being applied continuously in a single area for sufficient time to cause skin damage.
U.S. Pat. No. 7,170,034, issued Jan. 30, 2007 to Shalev et al., the entire contents of which is incorporated herein by reference, is addressed to an electric shaver comprising a heat element heated to a temperature sufficient to cut hair, the heating of the heat element being pulsed to prevent heat from being applied continuously in a single area for sufficient time to cause skin damage.
U.S. Pat. No. 7,202,446, issued Apr. 10, 2007 to Shalev et al., the entire contents of which is incorporated herein by reference, is addressed to an electric shaver comprising an elongated element heated to a temperature capable of cutting hair and a vibrating structure on which the elongated element is mounted, the vibrating structure arranged to prevent skin damage.
U.S. published patent application Ser. No. 2009/0205208 published Aug. 20, 2009 to Shalev, et al, the entire contents of which is incorporated herein by reference, is addressed to a hair cutting device comprising a detector adapted to detect motion of the shaver heated wire arranged to cut hair, a hair cutting removal and suppression head having a heated wire suitable for heating hair growing from the skin and cutting the hair, and a controller arranged to move the hair cutting removal and suppression head between a hair cutting position and a retracted position responsive to the presence of, or absence of, detected motion.
It is known that heating hair follicles affects hair growth rate. Experience has shown that repeated use of heat based hair removal devices, such as certain products available commercially from Radiancy, Inc. of Orangeburg, New York, reduces hair growth rate. Although hair growth rate is reduced by the above mentioned products, hair growth rate reduction is achieved as a byproduct, and is thus not optimal.
Follicular epithelial stem cells (FESC) are present within 0.5 mm of the skin surface in non-scalp skin. There is evidence that permanent thermal damage to FESCs are not specifically necessary to change the cell signaling between the FESC and the associated papilla, or that FESC are even involved in the induction of a catagen-like state that shuts down hair growth after injury to follicles. However, it is well known in medicine that subtle damage and stimuli can induce long-lasting biological inhibition in hair growth. These stimuli include mild hyperthermia; for example, fever can induce telogen effluvium, the loss of hair due to induction of catagen phase (the transitional phase between anagen and telogen lasting about 3 to 6 weeks). Other stimuli include hypoxia, oxidative stress, toxic chemical exposure, antimetabolites and radiation. The anagen (actively growing) hair follicle is ready to undergo apoptosis and its transition to telogen (resting) upon a number of triggers. This transition would not cause permanent hair loss, but would lead to long-lasting hair growth suppression, especially if the injury or stimuli were repeated frequently.
It would be desirable therefore to provide the benefits of such a long lasting hair growth suppression in cooperation with a shaver.